Optogenetics and other applications often require two or more independent optical images of different wavelengths or colors to be simultaneously projected onto the same specimen to optically stimulate the specimen. As an example, in optogenetics research, a blue image can be used to excite certain neurons while an orange or red image can be used to inhibit some other neurons.
In general, a spatial light modulator (“SLM”) may be used to generate an image to be projected onto a specimen. One conventional solution is to use multiple SLMs, where each generates an image of a single color, and then combine the images into a single image. An example of such a system is a three-panel color projector for display applications.
However, the use of a system having multiple SLMs has several drawbacks. Such system is expensive and requires a complex optical layout arrangement. Also, it is not particularly suitable for applications requiring a space-efficient compact design.
In addition, a conventional single-panel display system based on a field-sequential color, where, e.g., individual RGB images are displayed successively in a frame, operates at relatively low frequencies such as 60 Hz or 120 Hz. However, neuron responses are often faster than these low frequencies. For example, if colors were changed at a rate of 60 Hz or about every 17 ms, a typical neuron would be able to detect this 17 ms delay between colors. Therefore, a conventional single-panel display will introduce unwanted time dependence into experiments involving neurons.